The microsomal lipoprotein (MLP) fraction isolated from nitrogen decompression homogenates of mouse spleens or a cultured mouse lymphoblast L-5178Y, has proven to be an excellent source of H-2 and non-H-2 tranplantation antigens, as determined by an accelerated allograft test in vivo. The L-5l78Y MLP would immunize syngeneic mice to reject a tumor graft in vivo. Further studies are proposed for biochemical and immunological characterization of these antigens using the MLP as a starting material and detergents as a dissociating reagent. An assay is proposed to monitor autolytic degradation during biochemical fractionation. Purification procedures will be followed by a radioimmunoprecipitation assay that we have developed. To further analyze the allograft response in vivo and in vitro, assays for killer cells and a sensitive radioimmune assay for antibody have been developed. A new test for antigen-binding cells is proposed, in which a Beta-galactosidase-MLP complex, when bound specifically to cells and plated in agar with bacteria, permits bacteria to grow as "galaxy-type" colonies directly over the antigen-binding cells. The formation of each of these effectors will be followed in vivo during allograft rejection during sensitization with antigens and in in vitro models of the immune response. The versatility of the assay for cytolytic and non-cytolytic antibodies to cell surface antigens will be explored. Non-cytolytic antibodies to a tumor associated transplantation antigen (TATA) and other transplantation antigens are easily detected. Sensitivity of this assay will be greatly increased to determine if serum antibody to TATA is an indicator of tumor growth in vivo. BIBLIOGRAPHIC REFERENCES: Goldstein, L.T. and L.A. Manson. Specificity of the immune response in a L-5178Y-DBA/2 syngeneic mouse system. Transplantation Proceedings. 7:513-515, 1975. Manson, L.A., L. Goldstein, R. Thorn and J. Palmer. Immune response against apparently host compatible transplantable tumors. Trans. Proc. 7:161-164, 1975.